Phosphorus diffusion method for preparing silicon solar battery

Abstract

The invention discloses a phosphorus diffusion method of a silicon solar battery. The phosphorus diffusion method comprises the following steps: (1) placing a silicon wafer to be treated in a diffusion furnace and heating to 780-810 DEG C; (2) heating to 810-870 DEG C, and after the temperature is stable, introducing nitrogen carrying a phosphorus source and dry oxygen at the same time so as to carry out constant-source diffusion, wherein the flow of the nitrogen carrying a phosphorus source is 1-1.7L / min, the dry oxygen flow is 0.4-0.7L / min, the phosphorus source is phosphorus oxychloride, and the temperature of the phosphorus source is constant at 12-20 DEG C, so the surface concentration of phosphorus impurities on the surface of the silicon wafer is (1.0e+21)-(1.3e+21)cm<-3>; (3) keeping the diffusion furnace temperature and the dry oxygen flow unchanged, stopping introducing the nitrogen carrying a phosphorus source, and carrying out oxygen limited-source diffusion; and (4) cooling, and pulling out a quartz boat, thus finishing the diffusion process. The phosphorus diffusion method disclosed by the invention can be used for reducing the surface concentration of the phosphorus impurities on the surface of the silicon wafer, reducing the surface minority carrier recombination rate and improving the photoelectric conversion efficiency. Compared with an existing phosphorus diffusion process, the phosphorus diffusion method disclosed by the invention has the advantages that the absolute value of the increase of the photoelectric conversion efficiency of the obtained solar battery is 0.1%, and an unexpected technical effect can be achieved.

Description

technical field [0001] The invention relates to a diffusion junction process for preparing silicon solar cells, in particular to a phosphorus diffusion method for preparing silicon solar cells. Background technique [0002] A solar cell is a device that directly converts light energy into electrical energy. Because it is clean, non-polluting, inexhaustible and inexhaustible, it has gradually become an important power generation method. The principle is to use the photovoltaic effect of the PN junction to convert light energy into electrical energy. [0003] At present, silicon solar cells are widely used, and its manufacturing process has also been standardized. The main steps are: chemical cleaning and surface structuring (texturing) - diffusion junction - etching cleaning - deposition of anti-reflection film - printing electrodes - sintering. Among them, the step of diffusion junction (usually phosphorus diffusion junction) is a key step, and the junction process has a cr...

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Problems solved by technology

However, if the proportion of the source-carrying gas is too small, the mixing of the diffusion atmosphere will be insufficient and uneven, resulting in poor uniformity of sheet resistance and poor process controllability

[0005] In addition, for the tubular diffusion furnaces currently widely used in production, the main factors affecting the inhomogeneity between the plates are: unbalanced temperature distribution in the axial direction, mismatch of gas inlet and outlet, and serious heat dissipation at the furnace mouth; affecting the inhomogeneity in the plate The main reason is that there are differences in the atmosphere environment and temperature field along the radial direction

Therefore, in the case of insufficient and uneven mixing of the diffusion atmosphere, if only relying on the method of temperature compensation in different temperature zones, it is obviously far from being able to achieve an ideal uniform diffusion state, which will eventually affect the controllability of subsequent process parameters and the performance of solar cells. electrical properties

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